Railroad freight cars typically include an elongated car body supported toward opposite ends by a pair of wheeled trucks. Each wheeled truck includes a bolster laterally extending between two side frames with a wheel and axle assembly arranged to front and rear sides of the bolster. Each railcar also has a brake system operably associated therewith. A conventional brake system includes a brake beam assembly associated with each wheel and axle assembly and which is connected to brake rigging on the railcar. Each brake beam assembly is supported between the truck side frames to allow it to be operated into and out of braking positions in relation to the respective wheel and axle assembly.
One form of brake beam assembly commonly used in the railcar industry includes a compression member and a tension member arranged in a truss-like configuration with a strut extending therebetween. A brake head, with a replaceable brake shoe, is arranged at each end of the brake beam assembly. It has been found beneficial for the brake beam assembly to maintain both a degree of camber in the compression member and a degree or level of tension in the tension member.
Brake beam assemblies on the railcar are typically operated in simultaneous relation by a power source from a brake cylinder or a hand brake and, through leverage, transmit and deliver braking forces to the brake shoes at the wheels of each wheel and axle assembly. On a typical railcar, brake rigging, including a brake push rod, transmits force, caused by the push of air entering the brake cylinder or by the pull of the hand brake, to the brake shoes.
The brake rigging on the railcar, used to transmit and deliver braking forces to the braking shoes of each wheel assembly, comprises a multitude of linkages including various levers, rods and pins. For example, brake levers are used throughout the brake rigging on each car to transmit as well as increase or decrease the braking force on each wheel and axle assembly
A conventional strut on a railroad freight car brake beam assembly has a hollow center with two joined sides or walls, with one side or wall being arranged on opposite sides of a longitudinal axis of the strut. When assembled, the strut is operably connected to the tension and compression members proximate midlength of such members. A conventional brake beam assembly strut has an axially elongated and generally centralized, close-ended slot between the two sides of thereof. Typically, a central portion of a brake lever extends through and is pivotally mounted in the slot between the opposed sides of the strut. Besides being pivotally supported by the strut, opposite ends of the brake lever are articulately connected through suitable connections to the railcar brake rigging. About midlength thereof, the strut defines two openings or bores aligned along an axis extending generally normal to the longitudinal axis of the strut. A pivot pin passes endwise through the bores and through the central portion of the brake lever to define an axis about which the brake lever pivots during railcar operation.
To lower the upper end of the brake lever relative to the position it would occupy if the brake lever were vertical, such brake levers are inclined lengthwise of the brake beam a certain number of degrees, usually about 40°. The strut is designed to accommodate suitable inclination of the brake lever from vertical. To reduce strut wear and to facilitate operation of the brake beam assembly during operation of the railcar, it is known to provide the strut with two brake pin bushings seated in the bores of the strut and which journal the pivot pin for the brake beam.
During use, a railcar can travel tens of thousands of miles between locations and over railbeds, some of which can be in significant disrepair. During railcar travel, the brake lever and related parts of the braking system are subject to vibration and wear. Accordingly, it is not unusual for one or more of the brake pin bushings to unseat from its respective bore and separate from the strut. The inclination of the bushings from vertical, coupled with gravity, also tends to cause at least one of the brake pin bushings to remove itself from the respective bore in the strut. Moreover, current research shows the brake pin bushings are exposed to forces and components of forces acting in a direction working to unseat or displace the brake pin bushings from their respective bore and be driven the out of position relative to the strut.
In some designs, the brake pin bushings are fabricated from a powder sintered metal. Unless powder sintered metal bushings are properly seated within their respective strut bore, such bushings can crack as they become displaced from their respective strut bore. Moreover, and even if such brake pin bushings remain partially seated in the strut bore, the powder sintered metal bushing is prone to chipping. Wear on the brake pin bushings can change the disposition about which the brake lever pivots, thus, changing the pressure exerted by the brake pads to the railcar wheels. Moreover, and under the rules of the American Association of Railroads (the “AAR”), bushing wear and cracking can result in condemnation of the brake beam assembly.
For a myriad of reasons, railroad freight cars are routinely inspected. Part of the inspection process involves an analysis of each railcar brake beam assembly on the railcar. When a particular railroad freight car is identified as having a brake beam assembly requiring repair or replacement, the freight car requiring such repair is usually separated from the remaining cars in the train consist and, then, moved to a facility where such repairs can be affected. Only after a suitable repair facility has been identified and becomes available, can replacement of a condemned brake beam assembly be affected.
Replacing a railcar brake beam assembly, for whatever reason, can be a time consuming process. Moreover, the valuable time lost in separating the railcar with the condemned brake beam from the remaining cars in the train consist, coupled with the time lost in scheduling a repair facility to accomplish replacement of the brake beam assembly, and the valuable time lost in affecting the repair or replacement of the condemned brake beam, along with the time lost in having to move the car with the condemned brake beam to the repair facility for replacement of the brake beam assembly are other considerations and unrealized costs involved with replacing a condemned brake beam. Of course, during this entire time period, the railcar is removed from service. Replacement of the condemned brake beam must also include the time lost in joining the repaired car to a train consist directed toward the original destination of the repaired car.
Thus, there is a continuing need and desire for a strut assembly for a railroad freight car brake beam assembly designed to inhibit inadvertent axial shifting of brake pin bushings in a direction away from the axis of the strut assembly thereby reducing the likelihood of damage to the brake pin bushing and thereby reducing the time and expense the railcar can be out of service due to a faulty brake beam assembly.